The present invention generally relates to implantable pumps for medical uses and more specifically relates to an implantable piezoelectric pump for a remotely adjustable gastric banding system.
Adjustable gastric banding is a medical procedure which can provide a safer, more effective, and substantially less invasive alternative to conventional gastric bypass surgery for the treatment of obesity. It has been recognized that sustained weight loss can be achieved through a laparoscopically-placed gastric band, for example, the LAP-BAND® gastric band or the LAP BAND AP® gastric band.
Generally, the LAP-BAND® gastric band is placed about an upper portion of a patient's stomach to form a smaller upper stomach “pouch” and a stoma that restricts the passage of food into a larger lower portion of the stomach. When the stoma is of an appropriate size, food held in the upper stomach pouch provides a feeling of satiety or fullness that discourages overeating.
One highly desirable aspect of gastric banding procedures is that gastric banding procedures are generally performed laparoscopically, and are considered to be minimally invasive procedures, relative to more invasive “open” surgical procedures such as gastric bypass surgery. Consequently, gastric banding procedures may cause less discomfort to the patient and generally require a shorter recovery time.
In addition, gastric banding procedures are substantially entirely reversible. If a doctor and patient decide to remove the gastric band after placement, for example, in the event that the desired weight loss is not being achieved and/or the patient cannot adjust to new eating habits required as a gastric banding patient, the removal of the gastric band will likely restore the stomach to the original size and form. Unlike gastric bypass procedures, gastric banding procedures require no permanent surgical modification to the gastrointestinal tract.
It has been recognized that over time, the stoma created by the gastric band on the stomach may need adjustment in order to maintain an appropriate size. To ensure a desired weight-loss result and comfort to the patient, the stoma should be neither too restrictive nor too loose. Accordingly, hydraulically adjustable gastric bands, for example the LAP BAND AP® system, include an inflatable portion of the band which can be used to adjust the size of the stoma. The inflatable portion can be “inflated” or filled with saline to an increased volume, and “deflated” or drained to a decreased volume, to achieve the ideal stoma size. Filling and draining is accomplished through a fluid access port positioned subcutaneously in the patient. In other words, by adding or removing fluid to or from the inflatable portion, e.g. by means of a hypodermic needle inserted into the access port, a physician can adjust the size of an inner circumference of the band about the stomach.
Automatically adjustable hydraulic gastric banding systems, as well as remotely adjustable hydraulic gastric banding systems, have been proposed.
Birk, U.S. Patent Application Publication No. 2007/0156013, commonly assigned herewith and incorporated in its entirety herein by this specific reference, discloses an automatically adjustable gastric banding system including an adjustment assembly that includes a sensor for sensing fluid pressure in the inflatable portion of a gastric band. The adjustment assembly further includes an implantable pump connected to the expandable portion, and a controller for activating the pump to adjust volume of fluid in the inflatable portion of the band based on a sensed fluid pressure.
Birk et al. U.S. Patent Application Publication No. 2007/0265645, commonly assigned herewith and incorporated in its entirety herein by this specific reference, discloses a self-regulating gastric band adjustment assembly including an implantable fluid reservoir for containing a volume of the fluid useful for adjusting a gastric band.
Coe, U.S. Pat. No. 7,338,433, commonly assigned herewith and incorporated in its entirety herein by this specific reference, discloses a remotely controllable gastric banding system. The system includes a pressurized fluid reservoir coupled to an inflatable portion of a gastric band. Valves are provided for controlling fluid flow between the pressurized reservoir and the inflatable portion of the band. A controller is used to control the valves, thereby regulating the volume change in the inflatable portion of the band. The controller is remotely controllable from outside of the patient.
There has yet to be proposed a piezoelectrically driven pump which is straightforward in construction, and acceptably reliable and useful in an implanted environment particularly for use in the adjustment of gastric bands. The operability of a piezoelectric pump is highly dependent upon the environment in which it is operated. For example, piezoelectric materials such as ceramics are extremely fragile and highly sensitive. Ideally, a piezoelectric material used as an actuator for a pump must be kept in a moisture-free, non-condensing environment in order to remain reliable and operable. Polymers which are known to be biocompatible are not ideal materials as pump components because these materials tend to allow diffusion of water vapor. Further, as a result of even small changes in temperature and the relatively sealed nature of a pump implanted in a living body, liquid will tend to condense and accumulate in any pump space or void that is not absolutely hermetic.
While the various implantable pump systems which have been proposed appear to at least recognize the need for accurate and reliable technologies for maintaining a stoma size in a gastric banding patient, there still remains a need for more sophisticated implantable pump systems for use with remotely adjustable gastric bands. The present invention has been developed to provide an accurate, reliable, safe and highly sophisticated implantable piezoelectric pump system for medical uses, for example, for use in adjustable gastric banding systems.